Predicate Query

For any node in the graph _predicate_ queries for the name of all outgoing
edges.

Note that this is different to a schema or intent in designing a graph
because any given node might or might not have all the predicates that
other nodes have.

Something to try: query for the outgoing edges of some people from the
friends data and note how some have owns_pet listed and some do not.

In general, large graphs often represent a partial view of the
modeled data. Our job in analysis of the data is to understand the
relationships in the data while dealing with gaps or incomplete knowledge.